Petcock "burps" and Mikuni's leak

[sbelshe]

I have a '72 CB350 that is having some fuel issues. Neither are issues it seems until the bike sits for a few days.

First, my overflows on my Mikuni's leak... and keep leaking. I have left for a weekend and come back to over a pint of gas on the ground. And from what I can tell, it's both carbs. I bought the Mikuni's new and they have less than 100 miles on them and this has happened since before I even bought them. The old carbs leaked the same way. Usually overflow means a float issue, but these are brand new and I've taken them out and reseated them, same issue.

The second issue is with the petcock. Again, after sitting a few days, the petcock will start to almost "burp" and fuel will come right out of the face of it. I've replaced it, even tried using parts from old and new ones to Frankenstein one, same result. I first thought it was a pressure issue and the breather was bad, but I recently let it sit with the gas cap open, and it still did it.

No clue what's going on, and my friends with bikes have no idea either. Thoughts? Thanks.

 

[SONICJK]

Float height incorrect on the mikunis or a bad float needle or needle seat. Make sure you are using genuine mikuni parts and not cheap knock offs.

For the petcock the only possibility is a bad petcock or a bad seal to the tank.

 

[cxman]

if you have fuel out the hoses i bet you have fine sandy rust and crap in your gas tank

pull one of the 17 mm drain plugs off and lower it carefully out then look into the well of the drain and see if any junk is in there

 

[sbelshe]

SONIC, I bought the Mikuni's new from DCC, so assuming they are legit parts, but I have not checked the height.

cxman, my tank is moderately clean but not spotless, so gunk in the tank is definitely an option. Thanks alot, I'll give both a shot.

 

[cxman]

when ever fuel actually runs out the hoses in my carb kits it is always crap in the carbs so check carefully

i use a good fuel filter to help with this

like the emgo

http://www.ebay.com/itm/Emgo-Aluminum-Fuel-Filter-1-4in-Black-Anodized-14-34472-/331252200321?pt=Motorcycles_Parts_Accessories&hash=item4d202b7381&vxp=mtr

 

[plagrone]

Re: Petcock "burps" and Mikuni's leak

I spent a long time hunting an overflow leak. It ended up that the brass overflow tube itself had a hairline crack.

 

[sbelshe]

Thanks plagrone, I'll take a look there as well.

 

[cxman]

the mikuni does not have that tube cracking problem

its not like the kehins

 

[plagrone]

Re: Petcock "burps" and Mikuni's leak

the mikuni does not have that tube cracking problem

its not like the kehins

Ah, good to know

 

[sbelshe]

I didn't know the Kehins had that issue. Good to know for other projects.